UoH researchers find soil properties shaping root microbes of red gram

The Hindu

25-04-2025

Red gram (pigeon pea, 'arhar in Hindi, 'kandi in Telugu) often referred to as the 'poor man's protein', is an important staple crop that significantly contributes to the protein intake in vegetarian diets across many countries, including India.
Red gram thrives as a rainfed crop in the semi-arid regions of the world. Its roots form small and variously shaped nodules that engage in a symbiotic association with nitrogen-fixing bacteria, especially with 'Bradyrhizobium', one of the commonly known rhizobia.
University of Hyderabad (UoH) researchers led by Appa Rao Podile and his team from the department of plant sciences had conducted a comprehensive genome analysis to explore the factors influencing the microbe diversity within red gram nodules.
Different red gram genotypes like Asha, Durga, and Mannem Konda Kandi grown in different types of soils (Alfisol, Vertisol, and Inceptisol), as well as a wild relative of red gram in its native soil were examined for the study.
Red gram and other legumes as hosts benefit with the symbiotic association with the rhizobia, because the rhizobia convert atmospheric nitrogen — comprising over 75% of the air — into a form plants can use, thus reducing the need for external nitrogen fertilizers for small-scale farmers.
Nodules are not just filled with rhizobia alone, but several other microbes are also present in the nodules and around the nodules, which can impact the efficiency of the nodule in fixing atmospheric nitrogen.
They found the presence of non-rhizobial bacterial endophytes in the red gram nodules was evident all through. The position of the nodule on the root, the type of soil in which the red gram is grown, the variety and other environmental factors that contribute to the composition of the microbe nodule were revealed.
While the diversity of microbes in the nodule is less compared to bulk soil, it was more specialized, indicting the role of host selection. Another significant finding was that the microbes of the wild relative of red gram was dominated by 'Bradyrhizobium' while the cultivated varieties like Asha, Durga, and Mannem Konda Kandi had exhibited diverse bacterial communities.
In the process of domestication, the native symbiosis appears to have been compromised. The study also highlighted that soil properties played a more significant role than the host plant genetics in shaping the nodule microbes indicating the importance of soil.
The project was supported by the Science and Engineering Research Board (SERB), now known as 'Anusnadhan National Research Foundation' (ANRF) under the Department of Science and Technology (DST). Research students Anirban Basu, Chalasani Danteswari and PVSRN Sarma were involved in the work, said a press release.